I see soooooo many problems comming from growers using CFL's. Make sure your bulbs are at least 8-12" away from the plant. 12 for now, maybe 8 when you perfect your technique and develop a good room humidity. I only use 2 and your using 4 which means your producing ALOT of heat and I imagine you got impatient so you probably moved the lights closer. Keep it on 18, thats perfect. They need the dark time for root growth which is essential with CFL grows. Set the timer to a time when you'll be less likely to poke your head in there the dark period is actually very important. Also if your using a fan make sure its not blowing on the plants directly as that will dry the leaves out and cause them to burn faster and easier. I take it your new to CFL's, the low down essentially is they cant flower for a shit but their AMAZING for veg. So, keep the lights at 18-6 for as long as you can, train the plant. Trim it up, grow it out not up. You can do this by trimming excess foliage and pinching the top of the plant, then. Once its the ideal size you kick it into flower. Its very important that the first day of its 12 hour cycle ( Flower cycle ) that you give it some kind of flower boost. Usually 1mil/ 5 litters. ONLY the first day. At this point the last thing you want to do is burn your plants and throw all the months of hard work your about to endure to shit. Hope this helps.